Protists are primarily unicellular organisms that are not plants, fungus or animals, and are classified based on how they obtain their nutrition, and whether or not they are able to move. Animal and fungus-like protists are heterotrophs, which means that they do not make their own food and must obtain it from outside sources. Plant-like protists, such as algae, are autotrophs, which indicates that they produce their own food.
Animal-like protists include protozoans, which are classified according to if they move by flagella, pseudopodia or cilia. An example of a protozoan would be zooflagellates, which use one or two flagella to move. Some types of algae are protists. They are members of the protista family that act like plants, although some algae are true plants. Fungus-like protists include slime mold, and are decomposers that have an external digestion process.
Many protists reproduce asexually using binary fission. Others reproduce sexually in a process called conjugation. Most protists have specialized body parts that allow them to move, eat and digest food, remove excess water and reproduce. Some have a soft, flexible outer membrane while others are rigid and retain their shape.